Torsion-Box Workbench and Expandable Assembly Table

Torsion-Box Workbench and Expandable Assembly Table

Double your work space without doubling your shop space.

By Randy Johnson and Luke Hartle

In our shop, we used to pile tools, parts and hardware on top of a wobbly workbench made from 2x4s. When we had to glue a project together, we shoved everything aside. Finally, we got tired of searching for tools and space and set out to make a new style of workbench.

Our new workstation is two benches in one. The best part is a rolling storage unit that opens into a huge assembly table. Closed, it tucks right under the bench. We built the bench’s top as a torsion box, so it can span the distance over the assembly table without sagging. Both parts are made from home-center materials using simple joinery. Two work surfaces, lots of drawers and shelves—what a great excuse to buy more tools.

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The Workbench

A torsion box is composed of two sheets of plywood, or
skins, separated by a frame. The first step is to glue the outer
frames to the bottom skin. Clamping the parts to a flat surface,
such as these wooden I-beams, guarantees that the top will turn
out flat.

Cut the bridle joints on the inner torsion-frame parts with a
dado blade. You can cut them as a group by clamping them
against an auxiliary fence on your miter gauge.

Test-fit the inner torsion-frame assembly. It should slip into
place using hand pressure only. Then remove it, add glue
and reinstall it. Hold it in place by adding screws through the
outer frame parts.

Flip the assembly and screw the bottom skin to the
inner torsion frame. Then flip it back and add the top
skin. Keep the torsion box clamped to the I-beams during
each step to ensure that it stays flat.

Glue the trim boards to the torsion box. Install them
flush with the torsion box’s bottom. This will create a
recess on the top side for the removable work top to fit into.
Make long clamps by joining short clamps with couplers.

Install the work top. Screw it to the torsion box and use
wooden plugs to hide the screws. The top should fit
loosely into the recess, so it’s easy to remove if you wish to
replace it.

Use spacers to position the drawer slides for mounting to
the sides of the base cabinets. It’s best to mount the
slides before the cabinets are assembled, because it’s hard to
fit a cordless drill inside cabinets after they are put together.

Add levelers to the base cabinets if your shop floor is
uneven. These heavy-duty levelers are easily adjusted
from inside the cabinet through an access hole in the bottom.

The Expandable Assembly Table

The assembly table is composed of two identical cabinets. Joinery
is simple; it’s all held together with dadoes and biscuits.

Glue and clamp the door guides to the doubled-up top
and bottom. Doubling the top makes the work surface
extra solid. Doubling the bottom provides a strong place to
attach the wheels.

Install the hinged panels to the back of one cabinet,
using spacers to center the panel between the top and
bottom. The hinged panels must be installed perpendicular
to the bottom so they open and close square to the cabinets.

Attach the hinged panels to the back of the second cabinet.
Make sure the spacing between the hinged panels
on the second cabinet is identical to the spacing on the
first cabinet or binding will occur when you fold the cabinets
together. When the panels are folded together, the
panels fold into the recess at the back of the cabinets.

Install the wheels. The center wheels provide support for
the back of the cabinets and are offset from the middle of
the cabinet so they don’t hit each other as they swivel. Sash
locks hold the cabinets together when the table is folded up.

Measure for the removable top. You want the top to fit
snugly, yet be just loose enough to be pressed into place
using hand pressure.

Slip the sliding doors into the slotted guides. The doors
go into the deeper upper slot first and then drop down
into the shallow bottom slot. If the doors don’t slide freely,
reduce their thickness by sanding the back of the top and
bottom edges.

This story appears in American Woodworker January 2006, Issue #119.

January 2006, Issue #119.

Purchase this back issue.

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